Test: Cams - 2 - Mechanical Engineering MCQ

The pressure angle, representing the steepness of the cam profile, is the angle between the normal to the pitch Curve at a point and the direction of the follower motion. If varies in magnitude at all instants of the follower motion. A high value of the maximum pressure angle is not desired as it might jam the follower in the bearings.

The pressure angle of a cam is an important parameter in cam design, as it affects the force distribution between the cam and the follower, as well as the wear and tear on the components. Let’s evaluate each statement to determine which ones are correct:

1. Lift and type of the follower motion: The lift (or stroke) of the follower and the type of follower motion (such as uniform velocity, simple harmonic motion, or cycloidal motion) directly affect the cam profile and, consequently, the pressure angle. Therefore, this statement is correct.

2. Angle of ascent: The angle of ascent refers to the angle through which the cam rotates while the follower rises. This affects the velocity and acceleration of the follower and thus impacts the pressure angle. Therefore, this statement is also correct.

3. Offset between center line: If the follower is offset from the center line of the camshaft, it affects the geometry of the cam profile and the pressure angle. Hence, this statement is correct as well.

Since all three factors influence the pressure angle of a cam, the correct answer is: 1, 2, and 3

In a cam follower system, pitch joint is the point on the pitch curve at which the pressure angle is maximum.

Maximum speed = eωsinθ
= 1 x 2 x 1 = 2 cm/sec

For uniform acceleration and retardation the velocity of the follower must change at a constant rate and hence the velocity diagram of the follower consists of sloping straight lines. The velocity diagram represents everywhere the slope of the displacement diagram, the latter must be a curve whose slope changes at a constant rate. Hence the displacement diagram consists of double parabola.